The genesis of uranium ore with red alterations in the Nalinggou deposit, northeastern Ordos Basin, and its geological implications

The large-sized Nalinggou sandstone type uranium deposit was recently discovered in northeastern Ordos Basin. Distinctly different from the typical uranium deposits of interlayer oxidation zone type in the world, this deposit is characterized not only by the tabular or stratoid orebodies controlled by the interface between monolayer grayish green paleo-oxidized sand body and underling gray sand body but also by being far away from the roof and bottom plate. Part of the ore-hosting rocks appear macroscopically as reddish and charcoal debris-bearing ores and microscopically as special paragenetic mineral assemblages consisting of coffinite, hematite (goethite), pyrite and siderite. Based on the results of rock-mineral identifications, EMPA and acidolysis hydro-carbon decomposition analysis, combined with the results of the experiments and mathematic simulations for fluid barrier theory of uranium metallogenesis by former researcher, the authors hold that the Nalinggou uranium deposit resulted from interaction between oxidizing uraniferous brine and deep-seated reducing fluid and, furthermore, the changing of the oxidizing-reducing inter-face in the ore-forming process was the key factor for reddish alteration of ores, and the interactions between persistent strong oxi-dizing uraniferous fluid and weak deep-seated reducing fluid might have been the primary factor responsible for the formation of the tabular orebodies.